Now, I'm not a physicist, but from what I understand colour is a property of molecular structures. Now, we know that particles don't have colour.

So I guess good questions to ask you here would be :

1. Do you think the surface of an object is made only of colourless particles ?
2. Do you think that colourless particles alone can give rise to the property of colour, or there needs to be something else that has colour?
3. Are questions 1 and 2 about different things ?

Mr. Tremblay wrote: "Now, I'm not a physicist, but from what I understand colour is a property of molecular structures. Now, we know that particles don't have colour."

Unlike Mr. Tremblay, I am a physicist. Color depends on the wavelength of the radiation, or, in terms of photons, color depends on the energy of photons. If we want to discuss the colors of material bodies, we have to distinguish between radiated, reflected and transmitted light. If a body radiates light, the body's color is determined by the spectrum of radiated light. If a body reflects light, its color is determined by the spectrum of reflected light. If a body both radiates and reflects (which is of course, the common situation; the difference is in the relative intensities of radiation vs. reflection) the body's color results from the superposition of radiation and reflection spectra. Furthermore, if light is passing through a certain medium, it is partly absorbed so that the light coming out of that medium has a color determined additionally by the absorption spectrum of the medium. On top of that, the color, as our perception tells us about it, depends on the variable sensitivity of our vision apparatus to various parts of the spectrum. Regarding the question of what determines the wavelength of either radiated, reflected, or absorbed light, the first two depend on inter-atomic properties of the body, and the third on both inter-atomic and molecular properties of the material.

>
> "So I guess good questions to ask you here would be :
>
> 1. Do you think the surface of an object is made only of colourless
particles ?
> 2. Do you think that colourless particles alone can give rise to the
property of colour, or there needs to be something else that has colour ?"

Particles do not have a property which can be named "color" in the conventional sense of the term. (In physics of quarks a property called "color" is also used, but this term has noting to do with the term "color" as used in optics, the latter obviously being what Mr. Tremblay refers to). If bodies have color (in the sense of optics) it is because they radiate, reflect, and/or transmit electromagnetic waves in a certain range of wavelengths, or, in terms of photons, because they radiate, reflect, and/or transmit photons in a certain range of energies. The energy of radiated and reflected photons is determined by the electron structure of atoms, while the energy of transmitted photons is determined by both electron structure of atoms and that of molecules (and in some cases of clusters of molecules -- like the blue color of the sky which is due to the fluctuations of air density in the upper atmosphere, or the scarlet color of the sky at sunset which is due to the variable refraction of different wavelengths).

Mr. Tremblay continues:

"3. Are questions 1 and 2 about different things ?

> My answers to these questions would be yes, yes, and no."

Sorry, but questions 1 and 2 make little sense from the standpoint of physics, so if Mr. Tremblay wants to discuss the question of the relationship between the emergentist and the reductionist views, perhaps he has to come up with a different example. His argument, though, seems to be not against me but rather against Davies and other contributors to the anthology From Complexity to Life. Indeed, I have not made in my commentary to Davies's paper any assertion regarding the juxtaposition of the emergentist vs. the reductionist positions. Moreover, in my previous reply to Mr. Tremblay's letter, I wrote that in my view there is a whole spectrum of views on that relationship, with two mutually exclusive extreme positions and many intermediate ones. Perhaps it would make more sense if he writes up a commentary of his own to Davies's paper rather than continue commenting on my comments (although I certainly appreciate his interest in my commentary and wish him all the best).